This is a revision application under NOT-OD-09-058 entitled "NIH Announces the Availability of Recovery Act Funds for Competitive Revision Applications." In this application we propose to expand our research program in order to accelerate the development of a novel clinical candidate for the treatment of osteoarthritis (OA), a disease that currently affects 22% of the US population but has no effective treatment. The proposed expansion includes two additional collaborators, Dr. Richard Loeser at the Wake Forest University School of Medicine and Dr. Michael Peel at SCYNEXIS, Inc. The proposed budget includes salary support to hire or retain employees at all three institutions. The goal of the parent grant R43AR056911 is to develop a small molecule therapeutic that restores the ability of OA and aged chondrocytes to respond to growth factors. This growth-factor resistance is well-documented and is thought to contribute to the imbalance of matrix homeostasis that is the hallmark of OA. Treatment of primary bovine chondrocytes with IL-1 or TNF leads to a growth factor resistance that is similar to that described in aging and OA chondrocytes. Omeros has used the bovine system to identify two signal transduction inhibitors, from over 100 known inhibitors that were screened, that can completely restore the IGF-1 response to IL-1 treated bovine chondrocytes. The primary target for these two inhibitors is the same;however, the fact that other inhibitors with the same specificity cannot restore the IGF-1 response indicates that a second kinase target must be involved. The specific aims of the parent grant are a) to utilize siRNA knockdowns to identify the kinase target that inhibits the IGF-1 response, b) to determine if this kinase represents a global mediator of anabolic functions, and c) to establish clinical relevance of the kinase target by demonstrating efficacy of an active inhibitor in an in vivo OA model. In this revision application, we propose two additional goals that will significantly advance this project. The first is to confirm the clinical relevance of the novel kinase target by demonstrating that the same inhibitors can enhance the response of human OA or normal-aged chondrocytes to IGF-1 and/or TGF[unreadable], work that will be performed in the laboratory of Dr. Loeser. The second goal is to initiate synthetic chemistry efforts to define the structure activity relationships (SAR) around three lead chemical series in order to identify the most promising one for lead optimization and to facilitate target identification. Compound design and synthesis will be done by Dr. Peel and his chemistry team at SCYNEXIS, Inc. At the completion of this work we should have a) identified the kinase(s) that is responsible for cytokine inhibition of anabolic responses in bovine chondrocytes, b) validated the clinical relevance of this kinase in human OA and normal-aged chondrocytes and/or an in vivo rodent model of OA, and c) identified the most promising chemical series for the generation of a proprietary clinical candidate(s) with high potency and selectivity. PUBLIC HEALTH RELEVANCE: Currently, there is no effective treatment for osteoarthritis (OA), a severely debilitating disease that affects approximately 50% of those over 65 years of age. Our goal is to develop a novel therapeutic drug that can stimulate repair of damaged cartilage in the OA joint.